U.S. Pat. Nos. 5,958,266, 6,479,785, 6,787,730 and 6,867,387 describe methods and apparatus for incising tissue using plasma, and their separate disclosures are hereby incorporated by reference into the present application. These patents disclose how to generate and maintain plasma without using a traditional gas or liquid fuel (e.g., Argon, Xenon). Instead, these patents disclose how to generate and maintain plasma using atomic particles which surround the point of incision. Several of the patents describe a handpiece 26 with an incising electrode tip 28. In operation, the handpiece is grasped by the user (i.e., surgeon), and the incising electrode tip 28 is used to create an incision in tissue.
However, the above-referenced patents do not disclose a specific device and method for operating upon cardiovascular tissue utilizing plasma. Several U.S. patents disclose devices which utilize resistive heating (i.e., diathermy) to burn biologic tissue (such as cardiovascular tissue), but all of these devices suffer from the same drawbacks: they are all high-power devices which are difficult to control, thus resulting in the burning and destruction of unintended tissue.
Lasers have also been used to burn biologic tissue. For example, the process of ‘laser angioplasty’ has been used to burn away plaque within an artery. However, lasers suffer from some of the same problems as resistive heating devices (i.e., they are difficult to control and often damage surrounding tissue).
U.S. Pat. No. 7,070,595 recognizes some of the problems caused by resistive heating devices, and attempts to solve these problems through the controlled regulation of radiofrequency signal (i.e., microwave) emitted from an antenna coupled to the end of a catheter. However, although such a device may present some advantages over traditional resistive heating devices, the device still requires the heating of tissue to the point of destruction. Much like resistive heating, this type of ‘radiant’ heating requires high power levels, is not easily controlled, and results in the burning and destruction of unintended tissue. In essence, the device described in the '595 Patent works much like a microwave oven (and even operates in same frequency range as many microwave ovens: 900-2500 MHz), in that microwaves are used to heat tissue. Much like a microwave oven, the heating cannot be easily localized to a specific point within the tissue. Accordingly, the operator of such a device (e.g., surgeon) must be careful in his or her movements, so as not to destroy unintended tissue by accident.
Thus, there is presently a need for an apparatus which permits the simple and efficient incision and ablation of cardiovascular tissue using plasma.